A recurring problem in document handling operations is toner smudging or marking, which most often occurs as the result of the necessary interaction between document handling components and material units containing printed matter being handled by those components. The problem of toner smudging is especially acute and pervasive in document accumulation operations. In conventional accumulation configurations, a single-level accumulator drives material into and over entrance ramps with the use of o-rings (also known as polycords) that are continuously moving in the direction of material flow. These continuously moving o-rings contact each face (i.e., the front and/or the back side) of the material. The material is first driven, as separate pieces or a pair, into the accumulator from an upstream device. The material is then advanced to the exit end of the accumulator by the o-rings that are essentially designed to act as a slip drive and comes to rest as the lead edge of the material contacts a pair of output rollers. Subsequent pages then accumulate over or under each preceding piece until the accumulator's maximum capacity is reached (usually 10-15 sheets) or a full set is satisfied. The o-rings, however, continue to cycle as material comes to rest and as succeeding material enters the accumulator and begins to accumulate. Accordingly, toner smudge occurs as, for example, the bottom set of o-rings becomes impregnated with toner from preceding pieces and transfers this toner to the first page of the set as it rests in the static condition.
Examples of document handling devices such as accumulators that employ pressure-applying belts or o-rings to drive sheets are disclosed in U.S. Pat. Nos. 6,203,006; 5,915,686; 5,794,931; 5,775,689; 5,692,745; 5,655,761; 5,647,587; 5,590,873; 5,484,255; 5,244,200; 5,147,092; and 4,767,115.
Material removal can also be problematic in conventional accumulator devices. Material must be folded and often torn to be removed from between the fixed o-rings of the accumulator. Another problem relates to the stretching of o-rings over time due to wear and material removal. Moreover, material justification can be problematic, particularly when accumulating before a folder. To achieve a high quality fold with minimal shingling, a set of material that is square on all edges (front, back, and both sides) optimizes the fold quality. Other recurring issues include the ease with which an accumulator device can be changed from over-accumulation to under-accumulation, and can be adjusted to accommodate different material sizes, if such switching capabilities are provided at all.
The present invention is provided to address, in whole or in part, these and other problems associated with prior art document handling technology.